   (assoc ship :rotation-speed (+ rotation-speed rot)))
 
 (defn accelerate [{:keys [acceleration] :as ship} acc]
-  (assoc ship :acceleration (+ acceleration acc)))
+  (assoc ship :acceleration (+ acceleration acc)
+              :collidable? true))
 
 (defn toggle-shooting [ship do-shoot?]
-  (assoc ship :shooting? do-shoot?))
+  (assoc ship :shooting? do-shoot?
+              :collidable? true))
 
 ; ----------------------------------------------------------
 ; mutable model


      :direction      direction
      :rotation-speed rotation-speed
      }))
  ([size pos]
   (create-asteroid size pos [0 0]))

              (and (sequential? obj1) (sequential? obj2)) :seq-seq)))

(defmethod check-collision :map-map [obj1 obj2]
  (if (and (:collidable? obj1)
           (:collidable? obj2)
           (collide? obj1 obj2))
    [(assoc obj1 :hit? true) (assoc obj2 :hit? true)]
    [obj1 obj2]))

